DESCRIPTION: (provided by the applicant) A long-range goal of this research is to define the role of MeHPLA and nuclear type II sites in normal and malignant cell proliferation. The identification of MeHPLA as a ligand for type II sites which controls cell growth led to the development of MeHPLA-related compounds with antiproliferative activities and potential for the treatment of benign prostatic hyperplasia, endometriosis, breast and prostatic cancer. We recently identified the nuclear type II binding site as histone H4. This exciting discovery targets very specific genomic pathways for regulation by MeHPLA and related-compounds including bioflavonoids and phytoestrogens. These compounds bind to type II sites (histone H4) with high affinity and have classically been defined as antioxidants that scavage free radicals. Our recent data indicate very specific regulation of gene transcription at the level of chromatin structure and function by type II site (histone H4) ligands. Histone acetylation is temporally and functionally coupled to DNA replication and gene expression in experimental systems including uterus and cancer cells. We propose that MeHPLA and related compounds control normal and malignant cell proliferation by modulating chromatin acetylation patterns and core nucleosome unwinding by binding to histone H4. We will assess hormonal (estrogen, progesterone) modulation of histone H4 gene expression (mRNA and protein), ligand binding activity and cell proliferation in rat uterus and in ER-dependent (MCF-7 cells) and ER-independent (MDA-MD-231) breast cancer cells in vitro and when grown in nude mice (Specific Aim 1). Potential involvement of histones H1, H2A, H2B and H3 in ligand binding to histone H4 will be studied (Specific Aim 2). The identity of the ligand binding domain(s) on histone H4 by will be determined by protein sequencing and site directed mutagenesis studies (Specific Aim 3). Effects of MeHPLA and related histone H4 ligands on chromatin structure, histone acetylation, and steroid hormone-dependent chromatin remodeling and gene transcription in a cell free system (Specific Aim 4) will be assessed. Estrogen, antiestrogen and MeHPLArelated compound effect on the acetylation of histone H4 (or other histones), specific gene (cyclin Dl and p21) transcription and expression and cell proliferation (cell cycle transcition, etc.) in estrogen-dependent and estrogen-independent breast cancer cells in vitro and in vivo (Specific Aim 5) will be evaluated. The proposed studies should precisely define specific effects of MeHPLA and bioflavonoids on chromatin structure and function, growth related gene transcription and cellular proliferation in normal and malignant cells.